Mechanical pressure roasting of coffee

ABSTRACT

Green coffee either whole, flaked or ground is subjected to heat and a mechanical force preferably containing a shearing component sufficient to roast the coffee. The roasting produces a roasted coffee product having higher soluble solids whether atmospherically or pressure extracted compared to a conventional hot air roasts. The increased soluble solids content provides regular coffee wherein substantial reductions in the amount of coffee employed to prepare a brew are possible and in addition provides a soluble percolate of higher concentrations and at better yield in the manufacture of soluble coffee. The mechanical pressure roasting further provides improved controllable acidity but not in the order of that obtained by pressure roasting in the presence of large excesses of steam. The mechanical pressure roasting of coffee has been found to upgrade the flavor of Robusta-type coffees by removing typically tarry notes.

United States Patent [191 Mahlmann Oct. 2, 1973 [75] Inventor: James PQMahlmanRWaynQNJ.

[73] Assignee: GeneralFoods Corporatiomwhit Plains,N.J.

[22] Filed: Apr. 16, 1971 [211 App]. No.: 134,867

[52] U.S. Cl. 99/68, 99/66, 99/71 [51] Int. Cl. A23f 1/02 [58] Field ofSearch 99/68, 71, 69, 66

[56] References Cited UNITED STATES PATENTS 2,282,708 5 1942 Dantzig99/68 2,284,033 5/1942 Berry 99/69 3,655,398 4/1972 Pitchon et al...99/71 3,458,320 7/1969 Niven, Jr. 99/71 3,640,726 2/1972 Bolt et al99/68 3,511,666 5/1970 Hudson et a1... 99/66 X 3,634,094 1/1972 Ponzoniet al.. 99/68 2,716,936 9/1955 Kopf 99/68 X Primary Examiner-Frank W.Lutter Assistant ExaminerWilliam L. Mlentlik Att0rneyDaniel .1. Donovanand Thomas R. Savoie [57] ABSTRACT Green coffee either whole, flaked orground is subjected to heat and a mechanical force preferably containinga shearing component sufficient to roast the coffee. The roastingproduces a roasted coffee product having higher soluble solids whetheratmospherically or pressure extracted compared to a conventional hot airroasts. The increased soluble solids content provides regular coffeewherein substantial reductions in the amount of coffee employed toprepare a brew are possible and in addition provides a soluble percolateof higher concentrations and at better yield in the manufacture ofsoluble coffee. The mechanical pressure roasting further providesimproved controllable acidity but not in the order of that obtained bypressure roasting in the presence of large excesses of steam. Themechanical pressure roasting of coffee has been found to upgrade theflavor of Robusta-type coffees by removing typically tarry notes.

24 Claims, No Drawings 1 MECHANICAL PRESSURE ROASTING OF COFFEEBACKGROUND OF THE INVENTION This invention relates to pressure roastingof green coffee and more particularly to the roasting of green coffeesubjected to a mechanical force.'Still more particularly the inventionrelates to subjecting green coffee to a mechanical force having acompression force which results in compaction of thegreen coffeeduringthe roasting process and preferably in addition a shearing force whichinsures uniformity of roasting and controllable development of flavor,soluble solids, acidity, and other characteristics of the roastedcoffee.

Numerous roasting processes are known and employed in the roasting ofgreen coffee beans. Inconventional roasting the coffee beans are tumbledby mechanical means in the presence of hot gases which transfer heat tothe coffee beans through the medium of convection and increase thetemperature of the coffee beans to produce roasting to the desiredcolor. Improvements in the conventional system have been made employinghighvelocity hot gases to fluidize the coffee during roasting andaccomplish roasting in a period of several minutes or less. Such systemshave been found to produce an improvement in the water soluble solidsextractable from the roasted coffee.

Numerous patents describe variations of the commercial systems whereintheroasting gas is pressurized in order to lock in moisture andaromawhich are liberated during the roasting process. Such systems areexpensive to manufacture since the pressurized gases must be containedand in general give small improvements in the amount of available solidsafter roasting and small improvements, if any, in flavor. Still furthermodifications employ super-heated steam as the heat transfer medium andsuch systems are well described in the patent literature. Theseprocesses produce an appreciable increase in soluble solids but atthesame time appreciably increase the total titratable aciditypresent inthe roasted bean and decrease the pH of brews produced therefrom. Whilethe improvement insoluble solids is a worthwhile and desirable goal,these processes have not been extensively employed since the type ofacidity, and quantity of acidity developed during the roasting processhas downgraded the flavor of the coffees processed to the point wherethey were not desired by the consumer.

The prior roasting processes havelong sought a way of improving thedevelopment of soluble water solids produced in roasted coffee withoutadverse changes in acidity and pH which would make the beverageunacceptable to the consumer. The roasting art has long sought apressure roastingprocess which could develop additional soluble solidswithout the need for excessive amounts of water present or heavy-dutyroasters to contain the pressurized gas.

SUMMARY OF THE INVENTION The general purpose of this invention is toprovide roasted coffees of modified flavor and having a high solublesolids content without appreciable detrimental increases of totaltitratable acidity or pH of brews prepared therefrom and to provide aprocess for producing this new roasted coffee.

The roasted flavor modification and solublesolids improvements areachieved bysubjecting green coffee beans, either whole, flaked, ground,or in any other convenient form to a mechanical pressure or direct forceon the green coffee during the roasting process. The force appliedpreferably has components of both compression and shear, roasting beingaccomplished by the application of heat while the coffee beans aremaintained under the mechanical pressure.

The mechanical pressure roasting of coffee produces an unexpectedlyimproved roasted flavor for brews and percolate producedfrom low gradecoffees. In addi tion, for all types of coffee treated, mechanicalpressure roasting produces large increases in water soluble coffeesolids up to percent improvement (about 5 to 10 percent absolute orgreater), small and controllable increases in the acid level of thecoffee, better control on the final roast color or degree of roast ofthe green coffee, rapid roasting of the coffee generally in minutes orless, and a compressive and shearing disruption of cell structure whichincreases the roasted and ground density and causes other improvementsthat flow directly from the application of a mechanical force to thegreen coffee bean during the roasting cycle.

It is the object of this invention to provide a pressureroasting processdeveloping sufficient pressure while controlling the amounts of waterpresent during the roasting process.

It is a further object of this invention to provide a means for exertinga mechanical force of compression on green coffee beans during theroasting period in order to develop soluble solids and to modify theflavor of the coffees produced from the roast.

A still further object of this invention is to provide a means forexerting a mechanical pressure having force components of bothcompression and shear to compact and disrupt cells and to produce a.mixing effectwhich insures a uniform roast, a more uniform developmentof flavor and other desired attributes of the roasting process comparedto compression. roasting alone.

DESCRIPTION OF THE INVENTION The processes employed for the preparationof the new roasted coffee of this inventionrequirethat the green coffee,preferably whole bean, be subjected to a mechanical force containing atleast a component of compression which compacts the green coffee andinsures rapid heat transfer by conduction from heated surface contactingthe green coffee to the surface of the green coffee. The mechanicalcompression force, in addition to increasing the density of the coffeebeing subjected to roasting, disrupts the cells structure and produceschanges in the final roasted product that have long been desirable inthecoffee art. There is produced by compression roasting an increase inatmospherically available water soluble coffee solids of up to 10percent or more absolute and there is produced comparable changes in theyield of soluble coffeeprepared from to a component of compression, asthat normally obtained in a hydraulic press, a force of shear such asthat obtainable by using either screw or ram presses of the typeemployed in the plastics and food industries. The added component ofshear produces a desirable mixing action cuasing fast transfer of heatfrom the heat transfer surface pressing against the coffee, whichinsures uniform roasting and uniform development of flavor, solublesolids, acidity, and the like.

The process of this invention has unique advantages in the processing ofcertain types of green coffee. For example, in addition to improving thefinal water soluble solids content of low grade coffees such asRobustas, there is produced a completely unexpected improvement in theroasted coffee flavor of these low grade coffees. The objectionabletarry flavor characteristic of this coffee is removed. This allows anincrease of low cost or low grade coffees in both blends employed forregular coffee or for percolation in the production of soluble coffee.In addition, a controllable development of acidity allows acorresponding reduction in the amount of high grade or Colombian typecoffees employed in a blend.

In dealing with moderate priced coffee such as those available fromBrazil, a substantial increase in available water soluble solids isachieved while maintaining flavor at about that normally expected by theconsumer.

Of course, in addition to the use of the mechanically pressure roastedcoffee in blends, it is possible to make both regular and solubleproducts from a single variety of coffee employing the processes of thisinvention. Thus some of the cheaper types of vending machine coffee maybe substantially improved in flavor by employing mechanical pressureroasting. In addition to improvement in flavor, increased soluble solidsare obtained which allows reduction in the weight of roasted and groundcoffee necessary to produce a brew having the desired concentration ofcoffee solids.

Mechanical pressure roasting is also useful for treating milds typecoffee where certain changes are produced in roasted flavor that may beemployed to modify the flavor of roasted and ground products or solublecoffee. In addition, available soluble solids are increased allowingreduction in the amount of roasted ground coffee necessary to produce abrew.

Mechanical pressure roasting is also employed along with adjusting themoisture content of the green coffee to produce a variety of new coffeeflavors even when employing the high priced, Colombian type of greencoffee. By judicious adjustment of moisture content it is possible tomodify not only flavor but the extent of development of soluble solidsand acidity developed.

The processes of this invention have a further advantage in thetreatment of small and broken green coffee beans which are normallyscreened out prior to the conventional roasting of green coffee. Whereassmall size coffee is burned and high roasting losses occur duringconventional roasting, the processes of this invention allow roasting tobe carried out without appreciable loss of solids or development ofburnt flavors. For example, conventional roasts of small or brokencoffee beans incur losses greater than percent and many times nearly 30percent of the total green coffee roasted, whereas the present inventionallows roasting with a small incremental increase in roasting loss.

Prior to this invention, development of coffee-like flavor from flakedor ground roasted coffee was extremely difficult. There is a puffingeffect during the conventional roasting of green coffee which is notapparently obtained when ground or when flaked green coffee is roastedin a conventional manner. The processes of this invention haveparticular applicability in this area since a direct compressivemechanical force is applied to the surfaces of the green subdividedcoffee. Conduction of heat is rapid and roasting occurs in a shortperiod of time. Apparently, the mechanical pressure exerted allowsdevelopment of coffee-like flavors which have not heretofore beenpossible. Mechanical pressure with a force component causing shear ofthe green coffee is particularly preferred to provide better compaction,heat transfer, and uniformity of roast.

Mechanical pressure roasting provides a means for producing roastedcoffee products from many waste products developed during the normalprocessing of coffee. For example, chaff and other materials normallyremoved prior to roasting can now be roasted through the use ofmechanical force and heat. Green coffee can now be water extracted toremove green water solubles and caffeine, the caffeine removed, thegreen solids dehydrated and roasted by the processes of this invention.

Partially and totally extracted roasted coffee grounds can bere-processed to develop further soluble solids having coffee-likeflavor, employing the processes of this invention.

In addition to processing normally waste products from coffee, it is nowpossible to extract materials such as caffeine, coffee oil, or othermaterials from the green coffee by first subdividing the coffee toinsure substan tial increases in the rate of extraction and degree ofextraction. Once extraction is completed it is now possible, by thepressure roasting techniques of this invention, to develop regularcoffee flavor which has not heretofore been possible. For example, greencoffee may now be flaked as is done in the soybean industry, extractedwith a solvent having affinity for fat or oils such as benzene, hexane,trichlorethylene or the like, treated to remove the solvent, dehydratedto the best moisture content for flavor development, and mechanicallypressure roasted to develop a desirable roasted coffee flavor and aproduct having high soluble solids content. Green coffee can also besubdivided and the caffeine content removed by contact with either ariaqueous or organic solvent by methods generally known in the art. Onremoval of solvent residues, the green coffee can now be roasted underpressures sufficient to develop desirable coffee flavor and solublesolids. The dividing of green coffee beans not only speeds the rate ofextraction but reduces the amount of time under which the green coffeebean is subjected to heat and other process variables which adverselyaffect the flavor of coffee. Thus substantial improvements in flavor,soluble solids and other properties are possible by the application ofthe processes of this invention to ground, flaked, or otherwisesubdivided green coffee beans.

Mechanical pressure roasting can be applied to any whole green orsubdivided green coffee whether decaffeinated or otherwise treated ornot. Another advantage of this invention is the ability to reduceroasting loss normally occurring in hot air roasting by the applicationof mechanical pressure roasting. The exact mechanism is not understood,but is is believed that the mechanical pressure applied directly to thesurfaces of the beans traps about them and within them materials thatare normally lost in the conventional roasting of coffee. ln addition,closer control of roasting temperature is possible resulting in areduction of the variability in roast color and the number of roaststhat are normally burned during the commercial production of coffee.

Another chief advantage of this process is the possibility of producingnew forms of roasted coffee by pressing or otherwise molding the roastedcoffee into desired shapes. For example, pellets, doughnuts, or othergeometric shapes of roasted coffee can be prepared by mechanicalpressure roasting such as in a heated press or in an extruder employinga die to shape the final product. Mechanically pressure roasted coffeeis advantageous used in tea type bags and others such as Max-Pax brandregular coffee to give faster extraction of solids and greater brewconcentration.

As has been noted, the density of mechanical pressure roasted coffee isgenerally greater than that of conventionally roasted coffee. This is adesirable attribute for in addition to improved soluble solids content,there is a visual appearance that less coffee is being employed. Thiscould also be a drawback, however, in producing normal roasted andground coffee by this technique since the consumer has been accustomedto a certain density of coffee. The density differences can be overcomeby subjecting the roasted coffee to further processing. For example,modification of conventional grinding of coffee will produce a lighterdensity. lf grinding is not sufficient, the further reduction in densitycan be attained by subjecting the coffee to a vacuum or quicklyreleasing the mechanically pressure roasted coffee from a pressurizedsystem into the atmosphere or vacuum. If desired, agglomeration can alsobe employed to modify the density of the ground product.

A desirable advantage of this invention is to partially roast greencoffee employing mechanical pressure to a light roast color and thencomplete the roast using conventional hot air equipment. Alternatively,a complete mechanical pressure roasting may be followed by treatmentwith hot air,steam or the like to modify the roasted flavor such as byreducing the acid content of the roasted product.

The processes of this invention are carried out by subjecting greencoffee to a mechanical pressure and by supplying heat by conductiondirectly to the green coffee beans. The combination of mechanicalpressure and conductive heat insures a rapid roasting of the greencoffee and development of desirable coffee flavors as well assubstantial improvements in water soluble roasted coffee solids. Forexample, whole green coffee beans may be fed to an extruder having aheated barrel and heated shaft if desired. The beans are moved and mixedby the rotating shaft and heated by the hot walls contacting the coffee.Desirably, there is designed into the extrusion equipment a reduction inthe volume during extrusion which causes compaction of the coffee andshearing of the coffee during roasting. This insures rapid and uniformroasting and improves the soluble solids content obtained from thecoffee. It is possible, however, to design the extrusion equipment sothat the normal expansion of the green coffee during the roastingprocess causes the free volume within the extruder to be reduced to thepoint where there is a compression effect simply due to the green coffeeswelling and puffing without adequate volume to do so. Alternatively,green or roasted coffee may be placed between heated platens which arethen brought together, sandwiching the coffee between the plates. Thecoffee is subjected to the direct compression, and heat is transferredfrom the hot plates by conduction to the surfaces of the coffee. Again,rapid roasting takes place with substantial development of increasedsoluble solids content and modification of flavors. The type ofequipment employed is not critical. However, it is preferred to subjectthe green coffee to mechanical forces of both compression and shear toinsure uniformity of roasting and full development of the attributesproduced by this invention, namely, improved soluble solids, flavormodification, acid development, and the like. For purposes of obtainingboth compressive and shear force, the extrusion of coffee is preferredsince the rotating or plunging auger of the extruder both compacts andshears the coffee at least to the point of flattening and tearing aportion of the beans being roasted. The use of extrusion equipment alsoallows numerous variations in the design of the equipment to producedesirable results.

For example, green coffee, when fed into the extruder, may be subjectedto an inert atmosphere such as nitrogen, carbon dioxide, or the like,which will purge the oxygen from the extruder and insure mechanicalroasting in an inert atmosphere. By control of the quantity of the inertgas and coffee, substantial amounts of oxygen present during roastingmay be removed. In addition, an inert gas purge can be employed tomodify the amount of water vapor present in the roasting atmosphere. Ifdevelopment of acidity is not desirable, water vapor which contributesto acidity development can be removed by a gas purge.

Where soumess is not objectionable, the inert gas purge could beemployed as a carrier for additional water vapors to be added to theroasting environment. Control of the water and oxygen present during theroasting by control of the gaseous atmosphere present is easily obtainedduring extrusion roasting.

The extruder may also be modified by incorporating standard sections,anywhere on the barrel, for the application of a vacuum source to thesystem as is done in the production of certain food products, such aspasta products. This vacuum section could be employed to remove oxygenand water vapor or control the same as is done with the inert purge.

In addition to control of the roaster environment, the use of vacuum orinert gas may be employed to collect desirable aromas liberated duringthe roasting. This again is conveniently done in the extruder wherearoma collection can be precisely located. For example, grinder gasdeveloped during the roasting can be removed by application of a vacuumin the initial portions of the roasting section of the extruder. Roastergases can be removed at the discharge or near the discharge end of theextruder. When roasting low cost coffee such as Robustas, selection ofspecific points in the roasting process can be employed to removeundesirable flavor fractions from the roaster environment. Thus a vacuumsource can be attached to the extruder and used to remove theundesirable aroma components as they are developed during the roasterprocess. Of course, combinations of inert gas purge and vacuumtechniques can be employed where desirable.

A further advantage of applying mechanical pressure in an extruder isthe development of heat due to the compaction occurring within theextruder itself. Therefore, in addition to applying heat to either thebarrel or the rotating or reciprocating auger, it is possible to reducethe volume of the free area of the extruder and therefore compact thecoffee during roasting. The compaction and shearing force generates heatwhich in itself aids in the development of the desirable coffee flavorand soluble solids produced by the processes of this invention.

A further advantage of employing extrusion roasting is to simultaneouslyroast coffee and remove roasted coffee oil from the roasted product.This allows recution of the normal oil content of the roasted coffee andproduces a source of aroma which may be either returned to the resultingcoffee product or may be treated to isolate desirable flavor fractionswhich are in turn returned to the product. Oil removal can be attainedby fitting the heated barrel at the discharge end with a barrel of thetype employed in expellers so that oil is easily removed.

Mechanical pressure roasting has particular significance in reducingroasting time to five minutes or less and preferably from between twominutes to a matter of seconds.

In the examples that follow, green coffee is mechanically pressureroasted under conditions of both mechanical compression and shearemploying a Model 250 Extruder V4 inch, Catalog No. 398, manufactured byC. W. Brabender Instruments, Incorporated, of South Hackensack, NewJersey and described in bulletin LE 68. The extruder is recommended forplastics applications and has a inch barrel opening and a screw lengthto barrel diameter of 25/1 (L/D). The extruder barrel has three electricband heaters, 600 watts each. Temperature control is accomplished usinga Model 2500 extruder temperature control console manufactured byBrabender which has four heat zones, three for the barrel and one forthe die heater, when used, and four controllers for regulating barreltemperature up to 842C.

Coffee is placed in a small hopper cooperating with the opening to theextruder barrel. The coffee is pressed, using hand force on a rambetween the rotating flights of the extruder screw.

The coffee is conveyed by the rotating screw (auger) through the heatedbarrel of the extruder and allowed to discharge at the end of the screw.No die is employed but could be to exert greater mechanical force.Mechanical force is achieved by the natural expanding of the coffee asit roasts and by a tapering of the extruder shaft (where tapered shaftsare employed) which reduces the free volume between the barrel andscrew. Screws with a 1/1, 2/1 (Cat. No. 39-8A) and 3/1 (Cat. No. 39-88)compression ratio are employed and others are readily available athigher compression ratios. The extruder screws or augers arechrome-plated stainless steel, single flight, uniform pitch, having afeeddepth of 0.150 inches. The screw has 25 flights.

The feed rate of coffee passing through the extruder is regulated usinga variable speed drive and there is a device for measuring the motorload in amperes. Each of the barrel temperatures, zone No. 1, closest tothe feed, zone No. 2, intermediate between feed ad discharge, and zoneNo. 3 at the discharge end of the extruder are pre-set for the desiredroasting temperature.

The rate of coffee passing through the extruder is measured by weighingcoffee into, and out of the extruder. Green coffee is roasted within theheated barrel to any desired degree of roast. Conditions of flow rate,mechanical pressure, and temperature are easily adjusted to give coffeeof a specific roast color. Good grade coffees, such as Colombians, arenormally roasted to a low coffee color while low grade coffee such asAfrican or Indonesian Robustas are roasted to a light color.

The color of coffee is determined by grinding the roasted coffee andscreening it using U.S. No. 50 and pan. The portion that passes throughU.S. No. 50 and is retained on pan is collected, placed in a containerof l inch diameter and k inch deep and pressed under 1,200 psi with a 1inch ram. The pressed coffee is placed beneath a photoelectric searchunit of the color measuring device and the difference in reflected lightat 595 mu between a standard color plate and the coffee is indicated ascolor units on the scale of that instrument. When a lightly roastedcoffee is placed beneath the search unit, the light reflectance isgreater than the standard and the needle moves to a higher reading.

The color measuring device is a photoelectric reflection Model 610having a Model ylO-Y search unit, manufactured by Photovolt Company. Thestandard color plate employed is a ceramic plate of brown color and hue.The standard brown plate exhibits the following reflection curve usingmagnesium oxide to represent percent reflection.

REFLECTANCE Wave Length Percent Reflection mu The roasted and groundsamples are evaluated for flavor at a standard cup concentration of 1.35percent coffee soluble solids in the beverage. This is necessary sincemechanical pressure roasting develops far greater water soluble solidsthan conventional air roasting and if adjustment of concentration is notmade, the mechanical pressure roasted coffee flavor is too strong.

Brew solids are determined using a coffee hydrometer, described in TheDirect Reading Coffee Hydrometer, publication No. 61, The Coffee BrewingCenter, New York, New York (1970).

The roasted coffee available soluble solids are determined by grindingroasted coffee beans using the Hobart grinder to drip grind. Using a setof Tyler sieves, arranged as No. 14, No. 20 and pan, the sample isscreened, and the No. 20 screen fraction removed. The No. 20 fraction isused to determine the soluble solids. Approximately 5 i 0.0001 gms. ofNo. 20 screen fraction sample is transferred into a ml. Florence flaskby means of a brush. 75 mls. of distilled water are added. The flask isconnected to a water jacketed condenser and reflux for 2 '15 hours. Theresulting mixture is cooled and pressure filtered using Celite filteraid into a 200 ml. volumetric flask. Sufficient distilled water is addedfor two additional washings of the grounds. The contents of thevolumetric flask are brought up to volume with distilled water. Using a25 ml. volumetric pipette, the sample is transferred to a tared aluminumdish containing sand which has been previously weighed to the nearest0.01 milligram. The

contents are evaporated to near dryness on a steam bath, removed fromsteam bath, and further dehydrated in a vacuum oven maintained at 25inch Hg and 70C. The sample is removed from the vacuum oven, cooled in adesiccator and weighed on analytical balance to nearest 0.1 mg. Thesoluble solids content is determined by the following calculations:

A. (Final W gt. Initial Wgt.)=Wgt. of Soluble Solids residue in 25 ml.

B. (Wt. of residue) (200) (100) (Wt. of sample) (25) W=Soluble Solids(dry basis) pH and titratable acidity tests are run by preparing coffeebrews by conventional techniques and measuring the total solids contentof the brew. After cooling the brew to room temperature, 100 ml. of thebrew solution is transferred into a 200 ml. beaker. A pH meter iscalibrated using two known previously prepared buffer solutions. Afterrinsing the electrodes with distilled water, the electrodes are immersedin the coffee solution to beanalyzed. The initial pH is read andrecorded. The brew is titrated with a 0.1N sodium hydroxide solutionuntil the meter reads pH 8.10 and the ml. of hydroxide solutiondetermined and recorded. The titratable acidity is calculated by thefollowing formula:

=So1uble solids (as in basis) Roasting loss, as is and dry basis, iscalculated from the coffee weight processed and recovered andthemoisture content of the beans. Moisture content is determined by ovenmoisture by weighing about 5 to grams of whole bean or ground coffee(green or roasted) to the nearest 0.1 mg. into a previously taredaluminum dish with cover. The sample is placed in a forced draft oven at110C for 16 hours, then removed from oven, cooled in a desiccator andweighed. The moisture is calculated as follows:

Wgt. of Sample (Gross Wgt. before drying)(Tare Wgt.) Loss in Wgt. (GrossWgt. before drying)(Gross Wgt. after drying) H 0 [(Loss of Wgt.)(100)1/(Wgt. of Sample) Control roasts are made using a standard onepound Probat roaster.

The temperature of the extruder surfaces contacting the bean is notcritical provided a sufficient tempera ture of, say about 375F, isemployed to develop the desired roast color. High temperatures may beemployed provided sufficient shearing force is applied to uniformly mixthe beans and prevent local burning. This is achieved by eitherproviding a limited area between the heated surfaces and the coffee orby providing mixing zones within the extruder to continually mix thebeans during roasting.

Roasts made by mechanical pressure roasting have substantially highersoluble solids than Thermalo or Probat roasted coffee. The solublesolids content of the coffee produced by this invention. isnormallygreater than 30 percent and more generally from 30 to 41 percent,whereas conventional roasts contain a soluble solids content of from 24to 28 percent. Substantially greater cup strength is produced bymechanical pressure roasting as determined by either expert tasters orthe consumer. Thus mechanical pressured roasted coffee, when prepared ata recipe level of from percent to less than 75 percent, depending uponthe type of coffee employed, can equal cup strength produced from normalroasts employing a Thermalo roaster at percent recipe level. Inaddition, the processes of this invention .substantially upgrade theroasted flavor of low cost or low quality coffees such as Robustas, orthe like. The flavor quality of Brazilian or Santos beans is at least asgood as the conventional roasts while the high grade and expensivecoffees are modified in flavor but have substantially improved solublesolids content. Furthermore, the higher grade coffees after developmentof higher soluble solids can be later treated to reduce acidity, ifdesired, as was taught by post-treatment patents dealing with steam,pressure roasting of coffee.

Mechanical pressure roasting conditions are characterized by a confinedatmosphere in the application of both mechanical and gas pressure, withmechanical pressure being predominant; and by heat transfer by means ofconduction with some transfer by air and evolved gas convection. Themechanical pressure roasting of this invention also subjects the beansto compressive and shearing forces which disrupt cell structure and aidin compression of the coffee and improve the uniformity of roast colordevelopment during roasting. It appears that this combination ofcompressive and shearing forces and conductive heat transfer directly tothe green coffee bean produces a highly novel reoasted coffee havingdesirable flavor and improved characteristics such as soluble solidscontent.

Having described the general means for practicing this invention, therefollows specific examples which should not be construed to limit theinvention in any manner whatsoever but are intended merely to showpractical applications of this invention:

EXAMPLE I Green coffee beans and ground green coffee beans were eachprocessed through a heated laboratory extruder. The screw wasapproximately 7.5 inches long and three-fourths inches in diameter. Thebarrel was heated with electrical heaters to a temperature between 400Fto 500F. In some experiments, an additional heating zone was added byattaching a heated die to the end of the barrel. The coffee was fedthrough the extruder at a rate of 60 grams per minute at a screw speedof 50 R.P.M. Roasted product temperatures ranged from approximately 480Fto 535F and the coffee exited from a 0.5 inch die in the form of acylinder of coffee roasted to a degree where roast coffee flavor wasdeveloped. This experiment established that coffee beans, either wholebeans, flaked, or ground, could be roasted in a confined volume undermechanical pressure to generate roasted coffee flavor and produce afinished product having a new form and flavor. By application ofmechanical pressure to green coffee with heat, there is produced newroasted coffee products which can be employed as regular coffee orfurther processed into a soluble coffee. The above process may also beused to apply heat and mechanical pressure, with or without the additionof water, to upgrade low quality coffees.

The pressures employed in the above extrusion roasting were measured andgenerally fell between 300-800 psig.

EXAMPLE 11 A series of roasts were made employing the Brabenderextruder, Model 250, described in the specification.

Three augers-l/l, 2/1, and 3/1were employed. The l/l auger isconstructed so that if there is no change in the free volume, betweenheated barrel and auger, within the extruder. The 2/ 1 ratio auger isevenly tapered from feed to dishcarge, having a reduction in the freevolume within the extruder of one-half the feed volume at the dischargeend. The 3/1 auger reduces the free volume within the barrel at thedischarge end to one-third of the volume at the feed end.

Robusta type coffee from the Cameroons was employed in this experiment.For each auger a series of auger speeds were employed to vary the flowrate of coffee fed through the extruder and the retention time withinthe extruder. The barrel of the extruder was divided into three heatedsections. The first section closest to the feed port was maintained at400F, the second or middle section was maintained at 425F, and the thirdsection just immediate to the discharge was maintained at 475F. No diewas employed in this extruder and pressure was developed through theexpansion of the beans during roasting, and the reduction in freevolume' between the extruder barrel and auger for two of the threeaugers employed. The final temperature of the roasted coffee wasmeasured as it discharged from the extruder and the feed rate anddischarge rate of coffee recorded as well as the roast color of thefinal roasted coffee. Moisture data was obtained from the green androasted coffee and roasting loss (as and dry basis) was calculated forcertain of the runs. pH and titratable acidity values were determined aswell as soluble solids and brews solids. The results of the variousexperiments are tabulated below:

Auger Ratio: 3/1

auger speed R.P.M. 40 50 6O 70 probat control Roasted Coffee DischargeTem- 425 432 437 446 perature (F) Feed Rate (lbsJhr) 5.2 6.3 7.1 6.6Discharge Rate (lbs/hr) 4.4 5,8 6.5 6.0 Roast Color 59 74 82 80 kRoasting Loss (as is/ 6.6/3.7 8.1/5.2 8.1/5.9 8.8/5.6 dry basis)4.8/15.5 pl-l/TA 4.5/l7.6 4.7/14.9 4.8/14.9 4.8/15.5 Soluble SolidsBrew/Available 1.26/33.9 1.21/31.4 1.21/30.3 l.l6/29.4 Soluble SolidsAuger Ratio: 2/1 Auger Ratio: l/l auger speed RPM. 40 50 60 40 RoastedCoffee Discharge Tem- 428 436 338 perature (F) Feed Rate (lbs/hr) 5.56.2 Discharge Rate green, (lbs/hr) 5.1 5.8 Roast Color 54 55 58 notroasted A comparison of the data for augers 3/ l and 2/1 indicates thatat the same feed rate of green coffee and equivalent temperature withinthe extruder barrel, a lighter roast color is developed for the augerwith the greatest reduction in volume, namely, the 3/1 auger. Thisappears to be due to a reduction in retention time of the coffee passingthrough the heated extruder. At equivalent roast colors, however, thereis a trend to higher soluble solids content as the mechanical pressureapplied to the coffee is increased. Also, a comparison of the roastedbeans indicates the 3/1 auger roasted beans developed a roast of moreuniform character. The 1/1 ratio auger did not roast at the temperaturesemployed, most likely due to the absence of any appreciable shearingaction. Heat transfer appears to increase as the mechanical pressureincreases. In addition, the working of the coffee under compression andshear, the 2/1 and 3/1 ratio augers also generate heat which contributesto roasting. The net result is faster, more uniform roasts of the greencoffee under increased mechanical pressure.

Characteristic of the coffee produced by this invention is the shinycompressed surface of the roasted coffee compared to the normally dull,brownish color of conventionally air roasted coffee. Surfacecharacteristics indicate that mechanical compression and shear whileroasting has compressed and flattened the coffee and has produced a veryshiny surface characteristic.

Looking at the data for single auger roasts, one notes roast color to bea funtion of the time the coffee is subjected to the roastingtemperature. Roasting losses are seen to generally increase as roastcolor is decreased. Similarly, the lowest pH of brews and the highesttitratable acidity are found in the samples roasted to the lowest color.The soluble solids are also seen to increase with the darkening of thecoffee roast color. Roasting color appears to be a function of the timethe coffee is subjected to the constant temperature within the extruder.

EXAMPLE II] In an attempt to separate each of the variables affectingroasting under mechanical pressure, a hydraulic, heated press wasemployed having forces of compression but not shear.

A Pasadena hydraulic press having a fluid operated high pressure ramcapable of exerting a force of tons between 200 square inch heatingplates equipped with temperature control, was employed to determine theeffect of processing variables. The press permitted a high degree ofcontrol on roasting conditions, since it is equipped with automaticpressure and temperature regulation, but suffers from the defect ofbeing a compaction or compression roaster only and does not provide thebenefits obtained by having a component of force causing shearing of thegreen coffee bean during roasting.

Samples were prepared by mixing green coffee beans with dry ice, andgrinding in a Fitzpatrick comminuting machine using a No. 1 screen.After sublimation of the dry ice, the green coffee was ready forpressure roasting.

When a reduction in moisture was desired, the ground coffee was spreadon flat trays and placed in a Youngs Brothers drier at 140F for a timesufficient to remove the desired amount of moisture.

After grinding 100 grams of ground green coffee were spread evenly andthinly on a layer of cheesecloth on the top of a piece of aluminum foil.The cheesecloth and foil are folded over so as to make a by 10 inch flatpacket with aluminum foil on the outside. This packet was cold pressedin the Pasadena press to evenly distribute the coffee. To accomplishroasting, the packet containing green coffee was placed between thepreheated plates of the press and pressed. Thus at a.

rarn force of 70 tons, the actual pressure on the 100 square inch packetwas 1,400 psig. This pressure was employed except where noted otherwise.

During the entire course of roasting, the packet remained sealed but onrelease of the ram the packet exploded at the seal of aluminum foil,indicating gas pressure buildup within the roaster. The gas pressurewithin the packet was measured and found to be generally within 200 to300 psig by the end of roasting. The following variables wereinvestigated: green bean moisture, green bean particle size, ramtemperature, ram pressure, and roasting time.

Roasting Time. Medellin coffee was roasted by the preceding method. Anincrease in the roasting time was found to give roasts with greater cupstrength and higher soluble solids with optimum coffee flavor dependingupon other variables in addition to the roast time. The roast time wasvaried from 75 to 180 seconds. At the upper end of the time cycle,namely 180 seconds, objectionable burned notes were noted on flavorevaluation. This is due to the use of compression only. Mechanical shearhas been found to improve the uniformity of roast. The effect of roasttime on certain brew roast qualities is summarized below:

Roast Time Roast bean moisture of approximately 4% 65% recipe level Anexpert panel of coffee testers employed the following system inevaluating flavor and cup strength of Pasadena roasted beans compared toa conventionally roasted Thermolo roast control:

Quantitative Rating Extremely more or better Very much more or betterModerately more or better Slightly more or better Control Slightly lessor worse Moderately less or worse Very much less or worse Extremely lessor worse -NMJ MOQ 0 Due to their generally high cup strength, thesamples were prepared at 65 percent recipe level. A comparison of thePasadena roasts to the extrusion roasts indicates higher soluble solidsdevelopment with longer Pasadena roast times which correspond to thehigher Ram Temperature (F) 390 410 420 390 410 420 Moisture of GreenBeans 5.6 5.6 5.6 6.9 6.9 6.9 Roast Time (Seconds) 150 110 180 105 RamPressure (psig) 1400 1400 14001400 1400 1400 Roast Bean Soluble Solids35.4 37.0 36.9 36.8 38.9 39.5 Flavor Quality" 4.0 3.8 4.0 3.8 3.5 3.0Cup Strength" 5.0 5.5 5.5 6.0 7.0 8.0

** 65% Recipe Level The results from the previous section where roastingtime was the only variable showed an increase in soluble solids and cupstrength as the roasting time increased which was similar to that foundin extrusion roasting. While the roasting time as well as the ramtemperature was varied in the experiments, it can be seen that anincrease in the ram temperature gave greater soluble solids and cupstrength even though the roasting times were at the same time reduced.

Green Bean Moisture Content. The moisture level in the ground greenbeans prior to roasting affects a number of roasted beancharacteristics, some to a marked degree. Control of green coffee beanmoisture content can be employed to control the degree of acidity andsoluble solids development when roasting a variety or blend of coffee.Where little or no development of acidity is desired, the green coffeeshould be dehydrated to reduce the as is moisture content of the coffeeprior to mechanical roasting. Where development of acidity and highsoluble solids content is desired, the green coffee beans should behydrated. Modification of the green bean moisture content provides anopportunity to produce any degree of acidity desired. Modification ofgreen bean moisture prior to roasting can be employed for high costcoffees such as Columbians, medium cost coffees such as those fromBrazil or low cost coffees such as Robustas. The exact moisture contentfor a given variety of coffee or blend is easily determined and dependsto some extent on the other conditions employed in mechanical roasting.

The data on the following page was obtained for Me- Quality 5 P Strength5 4.6 5.0 5.5 5.5 6.0 7.2

Acid Flavor Note" 4.6 5.8 8.0 pH of Brew 4.90 5.00 4.75 4.58

"* 65% recipe level except for control As can be seen from the abovetable, a positive correlation was found between initial moisture leveland acid flavor level in the roasted beans. Green bean, as is, with amoisture content of about percent, produced brewed coffee with a highacid flavor level. Reduction in green bean moisture down to about 1percent, markedly reduced the acid flavor levels produced.

Trained flavor panel evaluations were consistent with pH measurementswhich showed an increase in pH with decreasing green moisture contentlevels. As noted previously, the aluminum foil packet containing thecoffee did not rupture until the ram was released at the end of theroast; and, therefore, unlike conventional themalo roasting, themoisture present in the green beans remained in immediate roastingvicinity throughout the roasting cycle. This moisture probably exists inboth the liquid state within the beans, and gaseous state in the freearea of the packet. Over the moisture range studied, higher moisturesgave higher soluble solids and greater cup strength.

Application of the same techniques to Robusta beans, where aciddevelopment is desirable, improves flavor while at the same timeimproves soluble solids and cup strength. It is apparent that beanmoisture content should be regulated depending on the type of the beanroasted, with high quality beans being roasted at lower moisture contentthan conventionally employed, and low quality beans roasted at moisturecontents greater than normally employed to control the acid developmentin the final roast.

The effect of moisture content on green whole Robusta beans wasevaluated by adding moisture to the green bean (6% H 0), and allowingthe beans to equilibrate. The beans were then roasted in the Brabenderextruder as in Example II employing a 3/1 auger and barrel temperaturesof 375F at the feed end, 400F intermediate, and 475F at the dischargeend. Control roasts were made using a one pound Probat roaster.

Roasted Percent Percent Control 1 lb. Probat roast R.C. H O S. T.A.

a... 6% H10 green 58 1.90 24.6 10.0 11% H O green 57 1. 60 24.7 7.0 14%H1O green 57 3. 00 25. 0 7. 6

Air quench.

No'rE.Flavora, b, and c all close in flavor-tarry, dirty, and earthy.

No'rE.Flavora, b, and e no Robustas tarry notes, (a) s1. sour, (b) sourand (0) very sour.

As in the Pasadena roasts, increased moisture content produced dramaticincreases in soluble solids, titratable acidity and cup strength.Unexpectedly, however, a marked improvement in the flavor quality of thelow cost coffee was also apparent. This data confirms that high qualitycoffee is preferably dehydrated to optimize flavor while low cost coffeemay be hydrated to further improve flavor. In each case, the applicationof mechanical pressure develops increased soluble solids reducing theamount of coffee necessary to prepare a roasted and ground brew or asoluble coffee product. Mechanical pressure roasts provide a 27 to 64percent increase in soluble solids while removing objectionable tarryflavor notes of Robusta or low cost coffee. The development of acidityand sourness can be controlled by the initial green bean moisturecontent.

Green Bean Particle Size. Pasadena compression roasts were made forvarious green bean particle sizes. The particle sizes investigated weredifferent Fitzpatrick Comminuting Machine grinds, flaked beans, andwhole beans. The results obtained, roughly from smaller to largeroverall particle sizes, are as follows:

Sample Number 1 2 3 4 5 No.3 Flaked No. Green No. 1 Fitz- Beans No. 3Whole Bean Fitzpatrick Roll Allis Beans Size patrick Screen ChalmersScreen Falker Green bean Moisture 3.1 6.9 3.1 8.6 6.9

Roast Time (seconds) 110 110 110 l 10 90 Ram Temperature (F) 410 410 4l0410 M0 Ram Pressure (psig) 1400 1400 1400 1400 1400 Roast Bean SolubleSolids 35.2 38.9 32.9 34.9 31.2 Flavor Quality 4.2 3.5 4.5 4.0 4.0 CupStrength 5.0 7.0 4.0 5.5 4.3

65% recipe level A trend appears to exist with finer particle size beansyielding somewhat higher soluble solids and greater cup strength. Morecoffee flavors of reasonable acceptability can be produced from all ofthe different particle sizes studied. Whole beans tended to char on thesurfaces and a burned note was present in these brews. However,application of both a compressive force and shear force, as wasaccomplished in a Brabender extruder, enabled whole coffee beans to beroasted to a uniform and improved flavor as is evident from laterexamples.

Mechanical Pressure. In contrast to conventional Thermalo roasting, oneof the strikingly different features of Pasadena Press and extruderroasting was the mechanical pressure applied to the roasting coffee. Ithad, in fact, been suggested that the greater soluble solids and cupstrengths of Pasadena Press and Brabender roasts were brought about bythe actual mechanical pressure on the coffee. A series of roasts wascarried out in which mechanical pressure (and where necessary, time) wasvaried. It was found that at lower ram pressures the rate of roastingdecreased (the time required to reach a given color end pointincreased). The following data was obtained on Medellin beans with allroasts taken to the same color end point:

Rarn Pressure (psig) 2800 1400 700 350 200 Green Bean Moisture (9%) 4.34.3 4.3 4.3 4.3 Roast Time (seconds)* 75 150 150 175 300 Ram Temperature(F) 410 390 390 390 390 Roast Bean Soluble Solids (70) 32.7 35.3 34.634.7 32.8 Flavor Quality" 4.5 4.5 3.4 2.5 2.0 Cup Strength" 4.7 5.0 4.03.5 3.2 65% recipe level Different roasting times were required toachieve the same color end point.

The above data showed that decreasing ram pressures resulted in lowersoluble solids, flavor quality and cup strength. It should be pointedout, however, that the soluble solids and cup strength remainconsiderably greater than that obtained by normal, conventional roastingof coffee. This data confirms the trend noted in extrusion roasting ofcoffee (shear forces also present) where soluble solids contentincreased as mechanical pressure was increased.

The exact mechanism producing the above results is not totally clear,but certainly would reflect the affect of pressure on the rate of heattransfer and, therefore, the rate of roasting as well as actualmechanical pressure on the coffee beans. Since it has been previouslynoted that decreasing roasting rates produced similar trends, some ofthe improvements in soluble coffee solids could be due to the time ofroasting. However, results of two roasts above where ram pressure wasthe only variable, coupled with the entire Pasadena and Brabenderpressure roasting studies, indicates that the affects noted above are toa degree a function of mechanical pressure itself.

The determination of the exact optimum force of compression and shear isroutine to one of ordinary skill in the art. However, the discovery andapplication of mechanical compression and shear during roasting isunexpected and a chief advantage of this invention.

EXAMPLE IV Low cost Robusta coffee was conventionally roasted in aProbat roaster and also roasted in the Brabender extruder. Analysis ofthe samples produced the follow ing results:

- Sample %H RC. pH/T.A. S.S. Control 1.9% 65 5.6/l0.0 24.5% ExtruderRoasted 4.2% 60 4.9/13.7 33.8%

a 38% increase in available 8.5.

The roasted samples were ground to a perc or regular grind using aHobart grinder and subjected to a single column extraction.Approximately 1,000 g. of roasted and ground coffee was placed in acolumn and hot water, at least 200F, passed through the bed of coffeeentering at the bottom of the bed and discharging at the top. Whenextract is observed exiting from the column, the discharge isinterrupted to bring the column and its contents to 10-14 psig. The feedwater is interrupted and the column maintained in a heated condition for25 minutes. After this holdup, the hot water feed is continued untilabout 1,000 g. of coffee extract is obtained, normally over a ten minuteperiod. The following concentrations were measured during collection ofthe ex- Mechanical pressure roasted coffee was found to give a 34percent increase in yield which, coupled with improved flavor for lowcost coffees, represents appreciable cost savings in the manufacture ofsoluble coffee. The extract from the above extraction, or conventionalcoffee extraction of mechanically roasted coffee, is dehydrated byconventional means such as spray drying, freeze drying and the like.

EXAMPLE V Robusta coffee was treated as in Example [1. A 2/1 auger wasemployed and a temperature profile of 380, 450, and 460F for zones 1, 2,and 3, respectively.

feed rate Brew Sol- (lbs/hr) RC Solids uble Flavor Solids 4.8 1.56 41Excellent upgrading,

good acidity, no earthy tarry notes 8.0 1.36 Clean, acid, green sourProbat Typical Robusta earthy, tarry flavor Control 70 0.96 28.3

When the temperature profile is changed to 385, 400, and 470F for zones1, 2, and 3, respectively, the

following results werev obtained:

5.1 74 1.38 37.6 Good cup quality-slightly 301.11

5.8 84 1.11 33.4 Definite upgrading compared to control When thetemperature profile is changed to 400, 425, and 475F for zones 1, 2, and3, respectively, the following results were obtained:

When Santosbeans are employed in place of the R0- bustas, largeincreases in soluble solids and brew solids are obtained.

When a decaffeinated green coffee blend (Sanka brand) is roasted at 390,430, and 445F for zones 1,

2, and 3, respectively, there was obtained a slightly under-roastedcoffee having a 50 RC. When this experiment was repeated lowering thetemperature in zones 1 and 2 by F, and increasing the zone 3 temperatureby 45F to 490F, it was necessary to appreciably increase the feed rateof coffee from a varidrive setting of 30 to 60 (8.0 lbs./hr.) to obtainthe same roast color. Increasing the discharge zone temperature (zone 3)was found to develop a burnt flavor, illustrating that small changes inroasting temperature can produce appreciable flavor changes.

Blends of green coffee and small and broken green coffee were roasted asabove and were found to have good roasted brew flavor. The small andbroken bean roasting loss was not as great as experienced forconventional roasts.

EXAMPLE V1 Robusta coffee was treated as in Example V. A l/l auger wasemployed with an extruder barrel temperature profile of 425, 470, and500F for zones 1, 2, and 3, respectively.

feed rate Brew Soluble (lbs/hr) RC Solids Solids pl-l TA 5.65 62 4.6517.0 Probat Control 60 5.05 10.9

The flavor of the mechanically pressure roasted sample was found to beclean, sour, and acid, but not dirty or earthy compared to the control.Appreciably higher barrel temperature was necessary to roast employingthe 1/1 auger.

When the temperature profile was changed to 475, 500, and 525F for zones1, 2, and 3, respectively, the following results were obtained:

Auger feed rate Brew Soluble RPM (lbs/hr) RC Solids Solids pH TA 30 4.042 1.36 29.8 4.5 16.6 32 4.2 56 1.26 29.8 4.6 17.9 34 4.8 64 1.12 29.84.7 19.4 36 5.3 70 1.12 27.8 4.6 17.4 38 5 9 74 1.11 28.3 4.4 14.9

Brew solids and acidity were developed and small increases insoluble'solids content were noted compared to the Probat roastedcontrol. Mechanical pressure was present using the H1 auger only throughexpansion of the coffee as it roasted. Greater mechanical pressureappears necessary to develop appreciable quantities of soluble solids.Unexpectedly, however, the roasting at low mechanical pressure didremove the tarry and earthy flavor normally characteristic of Robustacoffee.

When good grade coffee (Colombians) were roasted employing a temperatureprofile of 420+ 20, 470: 30and 470: 30F for zones 1, 2, and 3,respectively, similar results were obtained. The flavor of the coffeewas changed with more sourness noted.

EXAMPLE V11 Robusta coffee was treated as in Example VI. A 3/1 auger wasemployed and a extruder barrel temperature profile of 400, 425, and 475Ffor zones 1, 2, and 3,

20 Control 4.8 15.9 1.16

Appreciable acidity and soluble solids were developed as retention timein the extruder increased. All mechanically roasted samples werecharacterized as having good clean flavor lacking typical tarry andearthy Robusta flavor.

Control one pound Probat roasts of Robusta green coffee develop about23-26 percent soluble solids as indicated below:

RC Soluble Solids 45 25.3

Comparison of the Probat roasts to the mechanical pressure roasts aboveindicates development of appreciable soluble solids without appreciableincrease in acidity due apparently to the great mechanical pressureexerted on the beans during roasting.

EXAMPLE VIII A series of samples were prepared to determine the totalyield of soluble solids available from mechanically roasted coffee. Amechanically roasted sample having an eighty roast color (RC) and 4.7percent roasted moisture was prepared employing a 2/1 auger, a barreltemperature of 400, 430, and 480F for zones 1, 2, and 3, respectively,an auger speed of 45 R.P.M. and a feed rate of 4.8 lbs/hr. using theModel 250 Brabender extruder. A second sample was prepared having a 58roast color and 4.0 percent roasted moisture employing a 2/1 auger, anauger speed of 38 R.P.M., a barrel temperature of 400, 425, and 475F forzones 1, 2, and 3, respectively, and a feed rate of 5.0 lbs./hr. ofgreen coffee using the Model 250 extruder. Control roasts of the sameRobusta coffee were made employing hot air plant roasters. The followingdata was obtained:

Total Soluble Solids Yield Extrusion Roasted and Control RobustasRoasted Atmospheric Autoclave 801- Total Sol- Sample Soluble Solids ubleSolids uble Solids 80 RC Extrusion Roast 35.4 16.9 52.3 83 RC Control25.8 22.3 48.2 58 RC Extrusion Roast 36.1 13.6 49.7 60 RC Control 23.023.6 46.6

Results clearly indicate considerable improvement in the yield ofsoluble coffee solids may be obtained employing conventional percolationtechniques. 1f conventional yields are desired, then an increase inflavor quality is possible through use of lower temperature extractionconditions.

The amount of atmospheric and autoclave soluble solids was determined bygrinding and screening the roasted coffee to prepare a selected roastedand ground sample suitable for extraction, having 40 percent by weight 812 US Std. screen and 60 percent by weight-12 20 US Std. screen.

One part sample is mixed with four parts water and extracted at 212F for30 minutes. The mixture is centrifuged and the soluble solids content ofthe first recovered extract determined. One part cake fromcentrifugation is mixed with six parts water and maintained at about212F for ten minutes. The wash mixture is centrifuged and the solidscontent of the second recovered coffee extract determined. Theatmospheric soluble solids content is then determined by adding thesolids content of the first and second extracts.

The cake from washing is pressure extracted (autoclaved) using threeparts water per part of cake at 350F for thirty minutes. As before, afirst extract and cake is obtained on centrifugation. The cake is washedas before for ten minutes and a second extract obtained. The autoclavesolids is the total of the soluble solids determined for the first andsecond extracts.

The roasted coffee of this invention has great application to solublecoffee production. New flavor prodnets are possible. improvements inprocess throughout for percolation and grinders appears possible.Employment of conventional extraction conditions affords improvedoverall yield and higher concentration. For conventional yields ofsoluble coffee, the temperature necessary during extraction is lower andthe product quality is improved.

Special techniques of percolation are applicable, such as extractionwith dilute extract as described by Clinton, et al., US. Pat. No.2,915,403, issued Dec. 1, 1959; as well as high temperature extractionas described by Guggenheim, US. Pat. No. 2,915,399, is sued Dec. 1,1951.

High solids percolation employing intercolumn heating within a series ofextractors and/or reverseflow of extract through some of the extractorsoffers improved concentration of solids in recovered percolate; or ifthe same concentration is recovered, an improvement in product qualitythrough use of lower temperatures during extraction.

Dilute extraction as taught by Bowden, et al., U.S. Pat. No. 3,089,772,issued May 14, 1963 offers better removal of soluble solids, higherconcentrations of solids in the percolate or greater yield of solublesolids over that normally found with conventionally roasted coffee.

The differences between available atmospheric and autoclave solids inmechanically roasted coffee can also be utilized to improve percolationby employing split extraction techniques. For example, atmospheric andautoclave solids can be removed separately giving higher concentrationsof solubles than normally obtained in the atmospheric extract. Theautoclave extract is a smaller fraction of the total recovered extractand is easily concentrated and added to the atmospheric solids toproduce an extract of improved concentration and a resulting product ofimproved flavor. improved yield of solids is also possible if theconcentration of solids is not increased apreciably over that recoveredemploying conventional split extraction techniques. Split extraction isalso possible employing a pressure extraction of partially extractedcoffee from conventional rnulticolumn extraction. Here, the sameimprovements in concentration, flavor, and yield are possible.

Mechanical pressure roasting may also be employed to produce roastedproducts which result in reduced foaming during soluble coffeeprocessing and have improved extraction characteristics therefrom.

The processing of decaffeinated coffee and other coffees where pressureproblems occur in the percolators may also be improved by use ofmechanically roasted coffee.

EXAMPLE IX The affect of mechanical pressure roasting on various typesof green whole coflee was determined by preparing a number of samples ofvarious roast color using the same procedure as generally followed inExample ll. Control hot air roasts of the same roast color were comparedto these experimental samples. A fixed volume of the beans afterroasting was weighed for each of these samples and the bulk density ofthe whole roasted bean calculated. The whole bean was then ground in astandard coffee grinder set at percolator grind, and the determinationof bulk density was again made on the ground sample. The following datawas obtained:

Percolator Grind Density Change A Percolator Grind Density (g/c MP .329.3 l 4 .337 .345

Whole Bean RC Density (g/cc) MP Control Coffee Control .307 .319 .310.32]

Columbians Brazils +.022 -.005 +.027 +.024 Sanka Brand Blend Robusta-.O05 +.0ll .337 .273 .331 .286

8 l t 2 +.0 l 5 MP Mechanically pressure roasted Control Hot air roastedThe previous data indicates mechanical pressure roasting causes anincrease in the ground density of green coffee from about 0.005 g. percc to over 0.02 g. per cc. The degree of density increase is expected tobe a function of the amount of mechanical pressure applied to the coffeebean and the variety of coffee bean being roasted. The difference inwhole bean density over that of control is most likely due to its newform, for as previously noted, mechanically roasted coffee has a shinysurface appearance and a flattened form.

EXAMPLE X Roasted Coffee Temperature (C) 183 Retention Time (seconds) 50Green Coffee Feed Rate (lbs/hr) Obviously, changes in the roastingtemperature and in compaction produced by the rotating auger allowfurther variation in the feed rate and retention time of the coffeebeing roasted. In general, retention times between 20 seconds to 240seconds are adequate when roasting at a temperature of at least 375F andpreferably above 390? A preferred temperature range is from 390F to520F, and more particularly an average temperature of 420F to 490F.

4. The method of claim 1 wherein th coffee is subdivided green coffeebeans.

5. The method of claim 4 wherein the green coffee W fikKii/iifiFXL-fiiltll minim assumes FOR VARIOUS TYPES OF GREEN COFFEE Greencofiees, Probat and Extruder roasted product data Operating data forExtruder samples A Temperature, degrees Feed Percent R.L. Percentpercent rate, Sample R.C. H2O (D.B.) pH-T.A. S.S. S.S. RPM Zone 1 Zone 2Zone 3 Product #lhr. gggfigigggjg- :3 2'3 313 4:7-1110 gig 2e 40 450 490510 410 4.2 Cmmbianfl 4 8-14 9 29 40 440 475 495 397 4 2 Colombians-E 603. 6 5. 0 31. 4 Santos-P" 60 3. 4 5. 2 23. 9 sanmsm 63 4 6 4 2 4.7 22.036.6 53 40 400 440 480 395 6.1 fig ggggjg" 2 4. 7-18. 0 8 4s as 400 425475 392 a. 0 ggggggggjg- 33 Z"? 2-3 4-9-15. 0 g 4e 45 400 430 480 3984.8 Decalfelnated hlend 1 41 2. 9 7. 1 24. s g g i z g fi gg fig 2 kg4.6 24.1 g as as 390 430 4x0 392 7.6

eea ena e en I Decaffeinated blend-Em. as 6.8 6.6 l f 33.3 i 41 385 411389 Note.P=Probat air roasted coffee; E=Model 260 Brabender roasted 0 Anadvantage of mechanical pressure roasting is control of the type anddegree of development of acidity and sourness. The flavor character ofmechanical pressure roasted coffee acidity and sourness is morepalatable than products prepared under pressure employing a gaseousmedium containing water vapor. in prior processes, steam was employed torapidly transfer heat and roast the coffee. Unfortunately, this did notprovide a means for closely controlling the moisture content of thecoffee being roasted nor the roasting environment since the quantity ofsteam was fixed by other process variables such as roast color androasting time. Typical of the prior art pressure roasting patents areUS. Pat. No. 3,106,470, issued Oct. 8, 1963 to Spotholtz; and U.S. Pat.No. 3,088,825, issued May 7, 1963 to Topolian, et al.

The present invention utilizes mechanical pressure to insure rapidconductive heat transfer and confinement of the coffee during roasting.This allows close control over the water content of the green coffeebeing roasted and the roaster environment which in turn provides controlover the flavor and quantity of acidity or sourness developed.

The present invention also provides a confined environment not presentin other rapid roasting methods such as fluid bed roasting (see US. Pat.No. 3,1 12,439, issued Feb. 25, 1964 to MacAllister, et al.), whichapparently is necessary for appreciable increases in the quantity ofwater soluble coffee solids.

l claim:

1. A method of uniformly roasting coffee to increase soluble solids in aroasted product comprising:

a. charging green coffee to an extruder',

b. simultaneously subjecting the green coffee to heat, and mechanicalforces of compression and shear within the extruder effective to roastthe green coffee and effective to develop greater soluble solids thannormally produced by conventional roasting;

c. and recovering the roasted coffee.

2. The method of claim ll wherein the coffee is whole green coffeebeans.

3. The method of claim 2 wherein the coffee is partially roasted,sufficient to develop greater soluble solids than normally produced byconventional roasting and the partially roasted coffee is nextconventionally roasted to the desired degree of roast.

ofiee using 2/1 anger.

is pre-treated by extraction of naturally occurring caffeine.

6. The method of claim 4 wherein the green coffee is pretreated byextraction of naturally occurring oils.

7. The product produced by the process of claim 1.

8. The method of claim 1 in which the roasted coffee is extracted withwater to produce a waterextract having improved soluble solids contentover. conventionally roasted coffee extracted in the same manner.

9. The method of claim 8 in which the extraction is carried out torecover both atmospheric extractable and autoclave extractable solids.

10. The method of claim 8 in which the roasted coffee is extracted witha dilute aqueous coffee extract.

11. The method of claim 8 in which the coffee is extracted employingintercolumn heating.

12. The method of claim 8 in whichatmospheric and autoclave coffeesolids are removed separately.

13. The method of claim 1 in which low'cost coffee is roasted effectiveto reduce the tarry flavor normally associated with roasted low costcoffee.

14. The method of claim 13 in which the low cost coffee is Robusta.

15. The method of claim 1 in which the roasted coffee is further groundand packaged inla porous material effective to give faster extraction ofsolids during brewing and a greater brew concentration.

16. The method of claim 1 in which the roasted coffee is post-treated toreduce the acid content of the coffee.

17. The method of claim 1 in which roasting is carried out under aninert atmosphere.

18. The method of claim 1 in which the green coffee is pretreated tomodify the moisture content of the coffee.

19. The'method of claim 1 in which one or more coffee aromas areremoved.

20. The method of claim 1 in which the coffee being roasted is subjectedto a vacuum source during roasting to remove at least part of thegaseous roaster environment' 21. The method of claim 1 in which part, ofthe heat is developed by compaction occurringwithin the extruder.

22. The method of claim 1 inwhich coffee oil is removed during roasting.

23. The method of claim 1 in which'the development of acidity andsourness is controlled by controlling the of the coffee beans prior toroasting is controlled within green bean moisture content prior toroasting. the range of OF to 350F.

24. The method of claim 1 in which the temperature o 7* McC OY M.GIBSON, JR. MARSHALL D NN UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent), 0 Dated October 2, 1 973 Inventor) James nn' It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shownbelow:

In Column 7, Line 14, after "allows" and before "of" the word...recution... should read ...reduction...

Inf-Column 10, Line 4, after "invention" and before "greater the words.isnormally. should read .is normally.

In Column 20, Line 1, before "Control" add --Probat--.

In Column 22, Example x, Line 59, after "200" and before "73" ...7.7...should read ...7.6...

Signed and sealed this 20th day of August 197 (SEAL) Attest:

Attesting Officer Commissioner of Patents

2. The method of claim 1 wherein the coffee is whole green coffee beans.3. The method of claim 2 wherein the coffee is partially roasted,sufficient to develop greater soluble solids than normally produced byconventional roasting and the partially roasted coffee is nextconventionally roasted to the desired degree of roast.
 4. The method ofclaim 1 wherein th coffee is subdivided green coffee beans.
 5. Themethod of claim 4 wherein the green coffee is pre-treated by extractionof naturally occurring caffeine.
 6. The method of claim 4 wherein thegreen coffee is pretreated by extraction of naturally occurring oils. 7.The product produced by the process of claim
 1. 8. The method of claim 1in which the roasted coffee is extracted with water to produce a waterextract having improved soluble solids content over conventionallyroasted coffee extracted in the same manner.
 9. The method of claim 8 inwhich the extraction is carried out to recover both atmosphericextractable and autoclave extractable solids.
 10. The method of claim 8in which the roasted coffee is extracted with a dilute aqueous coffeeextract.
 11. The method of claim 8 in which the coffee is extractedemploying intercolumn heating.
 12. The method of claim 8 in whichatmospheric and autoclave coffee solids are removed separately.
 13. Themethod of claim 1 in which low cost coffee is roasted effective toreduce the tarry flavor normally associated with roasted low costcoffee.
 14. The method of claim 13 in which the loW cost coffee isRobusta.
 15. The method of claim 1 in which the roasted coffee isfurther ground and packaged in a porous material effective to givefaster extraction of solids during brewing and a greater brewconcentration.
 16. The method of claim 1 in which the roasted coffee ispost-treated to reduce the acid content of the coffee.
 17. The method ofclaim 1 in which roasting is carried out under an inert atmosphere. 18.The method of claim 1 in which the green coffee is pretreated to modifythe moisture content of the coffee.
 19. The method of claim 1 in whichone or more coffee aromas are removed.
 20. The method of claim 1 inwhich the coffee being roasted is subjected to a vacuum source duringroasting to remove at least part of the gaseous roaster environment. 21.The method of claim 1 in which part of the heat is developed bycompaction occurring within the extruder.
 22. The method of claim 1 inwhich coffee oil is removed during roasting.
 23. The method of claim 1in which the development of acidity and sourness is controlled bycontrolling the green bean moisture content prior to roasting.
 24. Themethod of claim 1 in which the temperature of the coffee beans prior toroasting is controlled within the range of 0*F to 350*F.